1. Field of the Invention
The present invention is a screw for use with a screw driver for inserting the screw into a substrate and a rescue driver for removing the screw from the substrate when it becomes stripped such that it cannot be removed from the substrate employing the screw driver.
2. Description of the Related Art
Currently, when a screw becomes stripped, it becomes difficult or impossible to remove the screw from the substrate in which it is fastened. In surgical applications, it would be desirable to be able to remove a stripped screw from the substrate in which it is fastened, such as for example from a bone in the human body.
The present invention addresses this need by providing a first embodiment screw and an alternate embodiment screw that are both capable of being removed from a substrate with a rescue driver after the screw has become stripped such that the screw driver that was used to install the screw in the substrate cannot be employed to remove the screw.
The first preferred embodiment of the invention employs a screw with a screw head that includes the normal head with a first indented area located centrally within the head and a second indented area located centrally within the first indented area. The normal head, the first indented area and the second indented area each is provided with grooves for engagement with a tool. The grooves provided on the first indented area are engagable by a screw driver specifically matched to the screw such that the screw driver is provided with mating ridges that insert within and engage the grooves of the first indented area so that the screw can be inserted into a substrate employing the screw driver.
The grooves provided on the normal head and on the second indented area are engagable by a rescue tool or rescue driver specifically matched to the screw such that the rescue driver is provided with mating ridges that insert within and engage the grooves of the normal head and the second indented area so that the screw can be removed from a substrate employing the rescue driver when the grooves provided in the first indented area become stripped so that the screw cannot be removed from the substrate employing the screw driver.
A second embodiment of the invention employs a screw that is provided externally with normal threads and the head of the screw is provided with a central female threaded channel that is reverse threaded from the external threads of the screw. A normal screw driver is used to install the screw in a substrate by engaging grooves provided in the head of the screw with mating ridges on the screw driver. In order to remove the alternate screw from a substrate when the grooves in its head become stripped, a reverse threaded rescue tool is used. The reverse threaded rescue tool inserts into the central female threaded channel and is rotated to engage the reverse threads of the channel. The reverse threaded rescue tool is tightened into the channel until it is fully engaged with the female threaded channel. At that point, the screw will rotate in conjunction with the rescue tool to back the screw out of the substrate.